Metalating rubber polymers

ABSTRACT

RUBBER POLYMERS WHICH ARE (1) HOMOPOLYMERS OR COPOLYMERS OR CONJUGATED DIENES OR (2) COPOLYMERS OF A CONJUGATED DIENE AND A VINYL AROMATIC MONOMER ARE METALATED BY REACTION WITH ALKYL OR ARYL SODIUM OR POTASSIUM IN COMBINATION WITH A LITHIUM ALKOXIDE. SODIUM OR POTASSIUM ALKOXIDE MAY ALSO BE PRESENT.

United States Patent 3,781,261 METALATING RUBBER POLYMERS Adel F. Halasa, Bath, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio No Drawing. Filed Feb. 3, 1972, Ser. No. 223,365 Int. Cl. C08d /02 U.S. Cl. 26094.7 2 Claims ABSTRACT OF THE DISCLOSURE Rubber polymers which are (1) homopolymers or copolymers of conjugated dienes' or (2) copolymers of a conjugated diene and a vinyl aromatic monomer are metalated by reaction with alkyl or aryl sodium or potassium in combination with a lithium alkoxide. Sodium or potassium alkoxide may also be present.

This invention relates to the metalation of rubber polymers which are homopolymers or copolymers of conjugated dienes containing 4 to 6 carbon atoms or copolymers of such a conjugated diene and vinyl aromatic monomer (such as styrene, etc.), using a sodium or p0- tassium hydrocarbon alkyl or hydrocarbon aryl together with a lithium alkoxide. The copolymers may be random copolymers or block copolymers. Sodium or potassium alkoxide may also be present. The metalated polymer may be used where other metalated polymers have been used, as in the production of copolymers by reaction with an alkyl halide.

The invention includes a novel procedure for the preparation of sodium and potassium alkyls.

The preferred sodium or potassium alkyl is one which contains 4 to 8 carbon atoms in a straight or branched chain, such as straight or branched chain butyl, amyl, hexyl, heptyl or octyl; the sodium or potassium hydrocarbon aryl may be, for instance, phenyl, tolyl, xylyl, naphthyl, anthracyl, styryl, alpha-methyl styryl, etc. Sodium or potassium n-butyl or t-butyl is usually employed.

There is art on the use of alkoxides in polymerization reactions, but not for metalation. See, for example, Forman 3,607,851.

{Wotford 3,294,768 and Strobel 3,331,821 disclose the use of organosodium and organopotassium compounds in combination with lithium alkoxides as initiators for butadiene and butadiene-styrene, etc., polymerizations.

We find in Naylor 3,492,369 this explanation of the functioning of alkali metal compounds for metalation:

The metalating agent is limited to organolithium compounds. Organosodium and organopotassium compounds are unsuitable because they undergo chain trans fer reactions Preferred compounds are the nalykyllithium compounds containing from 3-5 carbon atoms per molecule.?, (column 4, lines35-43.)

Experimental data are given below which support the above conclusions of Naylor.

According to this invention, sodium and potassium alkyl and hydrocarbon'arylcompounds which are known as-initiatorsare used for metalation by using 0.05 to 20.0 parts of sodium or potassium as alkyl or aryl initiator, per 100 parts of polymer with 0.1 to 50 to 1000 parts of lithium in the lithium alkoxide which alkoxide contains 1 to 20 carbon atoms; the preferred ratio of sodium or potassium to lithium is 0.1 to 100-500. One-tenth to 50 parts of sodium or potassium as alkoxide per 100 parts of polymer may be used with the lithium alkoxide. Alkoxides containing 1 to 20 carbon atoms may be used. A temperature of 0m 100 C. may be used. Any aliphatic solvent usually employed in polymerizing butadiene may Patented Dec. 25, 1973 be used. The sodium and potassium t-amylates and menthylates are readily soluble in cyclic hydrocarbon aliphatic solvents containing 5 to 8 carbon atoms, for example, and will generally be used in commercial operations because solutions of higher solute content may be used. If alkyl sodium is used, potassium alkoxide may be used with the lithium alkoxide; and if alkyl potassium is used, either sodium or potassium alkoxide or both may be used with lithium alkoxide.

The preferred alkyl reagents are n-BuNa and n-BuK. They must be very pure-purer than is obtained by the usual procedures. Preferred methods of preparation are represented by the following equations:

n-BuLl NaOR n-BuNa LiOR (hexane (eyclohexane (hexane/cyclo- (hexane/cyclosoluble) soluble) hexane hexane insoluble) soluble) n-BuLi KOR n-BuK LiOR (hexane (cyclohexane (hexane/cyclo- (hexane/cyclosoluble) soluble) hexane hexane insoluble) soluble) R preferably represents an amyl or menthyl radical.

Although cyclohexane is the preferred solvent, other cycloalkanes of 5 to 10 carbon atoms may be used. A temperature of -20 to 50 C. may be used and preferably a temperature of 10 to 25 C.

The reaction is preferably carried out in cyclohexane, and temperatures of 30 to 25 C. may be used. Lithium alkoxide is soluble in cyclohexane and remains in solution. n-BuNa and n-BuK are insoluble in hexane and precipitate out. After several washings with hydrocarbon solvent, the n-BuNa and n-BuK are obtained in a very pure state, greater than 99.5 percent.

Alternatively, a more usual reaction may be used, such n-BuCl+2Na nBuNa+NaCl This method may be used even though sodium or potassium chloride is present (as impurity) with the BuNa or BuK present in the reaction with the sodium or potassium alkoxide.

The preparation of the t-amylates or menthylates of sodium and potassium is represented by these equations in which cyclohexane is the solvent:

(Cyclohexane) Na HOB. NaOR (soluble) (Cyclohexane) K HOB KOR (soluble) R preferably represents t-amyl or menthyl.

The preparations are preferably carried out at -50 to 50 C. (and preferably 30 to 50 C.) in cyclohexane in which the t-arnylates and methylates are soluble.

The invention is illustrated by the following examples. The polybutadiene used was a rubber polymer derived with butyllithium initiator.

EXAMPLE 1 Preparation of potassium t-alkyls ,To a 28-02. bottle containing 400 ml. of cyclohexane, was added .05 mole of potassium t-amylate. (Potassium t-amylate 'is prepared according to any standard procedure published in the literature, as by adding potassium metal to tert-amyl alcohol in hydrocarbon solvent.) The arated from the cyclohexane solvent which may contain METALATION OF POLYMERS a minoramoqnt f hexane 9 other aliphaflc hydrocarbon The polybutadiene referred to in the following example solvent in which the potassium t-amy late is prepared. The may be prepared by any known method as long as it is precipitate is washed several times with cyclohexane. The f of moisture and active hydrogen compounds that n-butyl potassium was placed in a 28-oz. bottle containdestroy the catalyst ing 400 ml. of cyclohexane where it was dispersed and EXAMPLE 3 used in the metalation of rubber.

An analysis Of the Solid flame Pmmetry hex arf ifiiidr e 23.122211?21122315531531'oi Potasslum metal present m 99 9 percent punty Tltra Ion bottle. To thls solution 1s added 6 mllllmoles of n-butyl of the solid, using the Gilman procedure, analyzed for potassium or sodium p p according to Example 1 -b t t 95 percent carbon bound potasslum as n u yl p0 assmm or 2. ThlS is dispersed in a larger amount of cyclohexane g i zggg g z jgl gggff as above the followmg to produce a solution blend which is essentially cyclohexane and thus a solvent for the sodium and potassium alkoxides which are used. To this is added 10 millimoles Metal y g p Pwity of lithium t-butoxide in hexane and the preparation is K tert Buty] 99 5 placed in a 50 C. polymerization bath for 6 hours. K g c gggi 33-2 In order to determine the efiiciency and elfectiveness of the metalation, the metalated polymer was treated with 12 ml. (18%) of freshly distilled styrene and placed in the 50 C. polymerization bath for 4 hours, in order to Any one or a mixture of these may be used instead of determine the extent of the metalation. The styrenated n-butyl potassium. copolymer was then recovered by coagulation and sta- EXAMPLE 2 bilized with antioxidant. It was analyzed by IR analysis to determine the styrene found, and examined for homopl'epal'atlon of Sodlllm alkyls styrene content by gel permeation chromatography. The

ercent of rafted st rene was found 'b difference. The Procedure of Example 1 was followed except that p Metalatio n efficien cy and efi'ectivene s are defined, as sodium t-amylate was dissolved in cyclohexane. After follows: complete addition of the n-butyllithium the solid which M t m precipitated out (which was n-butyl sodium) was collected e e cleny Po1ystyrene grafted in the same manner as described for the potassium com- +homostyrene pound in Example 1. It was shown upon analysis with M l 1 t d flame-photometry spectrum to contain 99.95 percent so- 1 nca cu a e dium. The Gilman titration gave 95 percent carbon- Meta anon eflaectlveness Mnfound bound sodium. This solid was placed in cyclohexane and See Table I for the conditions of ten different reactions,

Polystyrene grafted dispersed 1n 1t and then used for metalation of polymers. with the results.

TAB LE I Example- 3 4 5 6 7 8 9 10 Polybutadiene, parts- 100 100 100 100 100 100 100 100 n-BuK, parts- 0. 078 0. 156 0. 234 0. 312 n-BuNa, parts. 0. 046 0.092 0. 138 0. 184 t-BuOLi, parts* 0. 07 0. 14 0. 21 0. 28 0. 07 0. 14 0. 21 0. 28 Metalation time, ho 3 3 3 3 3 3 3 3 Metalation temp., C- 50 50 50 50 50 50 50 Styrene added, Hams 30. 0 30. 0 30. 0 30. 0 30. 0 30. 0 30. 0 30. 0 Percent styrene found by IR analyS S 16 17. 9 15. 7 18 16 17. 9 15.7 18 Percent metalation efliciency 93 95 97 95 90 97 100 100 Mn- (Number average molecular weight of styrene block grafted):

Found (G.P.G.)- 92, 000 54, 000 65, 000 52, 000 29, 000 60, 000 69, 000 60, 000

Calculated 15, 000 7, 500 5, 000 3, 700 15, 000 7, 500 5, 000 3, 700 Percent metalation efiectiveness 16. 80 7. 20 7. 69 7. 11 51. 72 12. 50 7. 24 6. 16

Parts are calculated as based on metal only.

The following sodium alkyls were prepared according to the foregoing procedure:

Metal Alkyl gr p P rity EXAMPLE 4 N a tert-Butyl 99. 5 g2 g gl In similar runs, lithium t-butoxide was added, as y p y indicated in Table II. The metalatlon effectiveness was Any of them may be used in the metalation described. materially increased.

TABLE II 'Fxa'mnle 1 2 3 4 5 6 7 8 Polybutadiene, par 100 100 100 100 100 100 100 100 Emmn'la 1 2 3 4 5 6 7 3 Polybutadiene, parts 100 100 100 100 100 100 100 100 n-Butyl potassium, parts- 0. 0078 0. 0156 0. 234 0. 312 n-Butyl sodium, parts*-- 0. 046 0. 092 O. 138 0. 184 t-BuOLi, parts" L0. 07 0. 14 t 0. 21 0. 28 0. 07 0. 14 0. 21 0. 28 t-Amyl-ONa, parts* 0. 046 0. 092 0. 138 O. 184 t-Amyl-QK, parts 0. 0078 0. 0156 0. 234 0. 312 Metalation time, ho 4 4 4 4 4 4 4 4 Metalation temp., C 50 V50 & 5O 50 50 50 50 50 Styrene added, par 20. 0 20.0 20. 0 20. 0 20. 0 20.0 20. 0 20.0 Percent metalation elficiency 30 50 8O 20 30 90 Percent homostyrene content- 70 50 40 20 70 30 10 M11- (average number molecular weight of block styrene grafted):

Found (G.]?.O.) 70, 000 64, 000 25,000 35, 000 22, 000 28, 000 33, 000 55, 0 Calculated 10, 000 5, 000 3, 000 2, 500 10, 000 5, 000 3, 000 2, 500 Percent metalation efiectiveness 14. 28 7. 81 12. 00 7. 14 22. O0 17. 80 9. 00 4. 54

Parts are calculated as based on metal only:

I claim:

1. The process of metalating rubbery polybutadiene which comprises treating 100 parts of polybutadiene with (a) 0.05 to 20 parts of potassium or sodium as potassium or sodium alkyl or a mixture thereof, the alkyl group containing 4 to 8 carbon atoms, (b) 0.1 to 1000 parts of lithium as lithium alkoxide and (c) 0.01 to 50 parts of sodium or potassium as alkoxide in solution in an aliphatic hydrocarbon solvent at 0 C. to 100 C., the alkoxides containing 1 to 20 carbon atoms.

2. The process of claim 1 in which sodium or potassium t-butyl is used with lithium butoxide and sodium or potassium t-amylate or menthylate, and the solvent is cyclohexane.

References Cited FOREIGN PATENTS 5 873,656 7/ 1961 Great Britain 26094.2 1,478,225 3/ 1967 France 260--877 X 1,144,151 3/ 1969 Great Britain 260877 X JOSEPH L. SCHOFER, Primary Examiner 10 W. F. HAMROCK, Assistant Examiner 22 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,781,261 Dated December 25, 1975 Inventofl Adel F. Halasa It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line 5'1, quotation marks should, appear at the beginning of the line.

Column 2, Line 55, "methylates" should be -menthylates-. Columns 5 and 4, Lines 60 and 6'1 should be deleted.

Column A, Line 75, "55,0" should be --55,o00--.

(SEAL) l v T I Atte st: I.

EDWARD' M.FLE OHEE,JR. e I 0. MARSHALL DANN Attesting Officer Commissioner of Patents 

